Hydraulic cylinder



Dec. 10, 1968 M NADDELL HYDRAULIC CYLINDER 3 Sheets-Sheet 1 Filed June10, 1966 INVENTOR. mww/ Wade e A 7' TORNEJL Dec. 10, 1968 NADDELL3,415,169

HYDRAULIC CYLINDER Filed June 10, 1966 3 Sheets-Sheet 2 N, I A I A A 3!'INVENTOR- iazzzze/ fiaaa el/ Dec. 10, 1968- M.NADDELL 3,415,169

HYDRAUL I C CYL IND ER Filed June 10. 1966 a Sheets-Sheet 5 IN VEN'TOR.

BY Wazzzze/ (701221 Jgfiw A 7' TOR/E):

United States Patent 3,415,169 HYDRAULIC CYLINDER Manuel Naddell, VanNuys, Califl, assignor, by mesne assignments, to Euclid, Inc., acorporation of Ohio Filed June 10, 1966, Ser. No. 556,742 7 Claims. (CI.92-85) ABSTRACT OF THE DISCLOSURE A hydraulic cylinder having a pistonmember formed with first and second passages which respectively connectwith the piston head end and the rod end of the cylinder. A valveassembly for decreasing the speed of cylinder contraction is located inthe first passage and includes an open-ended flow control valve slidablymounted in the passage and formed with a plurality of elongated slots. Aspring biases the flow control valve whereby the slots are locatedoutside of the associated passage when the cylinder is expanded. Duringcontraction of the cylinder, a boss formed with the cylinder is adaptedto block one open end of the flow control valve and urge the latteragainst the influence of the spring into the passage so that fluid fromthe piston head end of the cylinder is exhausted through the slots at adecreasing rate.

This invention concerns a hydraulic cylinder and more particularly avalving arrangement that provides a cushioning effect when the cylinderapproaches the end of its stroke.

The invention finds particular applicability, although not exclusive,with a hydraulic cylinder of the type used for raising and lowering thedump body of a dump vehicle. In this connection, when a loaded dump bodyis raised about its pivotal connection with the vehicle, near the end ofthe raising cycle the center of gravity of the dump body often movesovercenter so as to cause a quick extension of the hydraulic cylinder.This results in the final stage of the cylinder being jarred when thelimits of cylinder expansion are reached and frequently causes damage tooccur to the cylinder or the cylinder supports. Similarly, cylinderdamage can occur during the lowering cycle because the weight of thedump body will tend to increase the speed of cylinder contractionthereby causing a high vacuum to form at times inside the cylinder withresultant seal damage.

Accordingly, a principal object of the invention is to providecushioning means for a hydraulic cylinder so as the latter approachesthe end of its operating cycle, the speed of expansion or contraction isdecreased so as to prevent damage to the cylinder.

Another object of the invention is the provision of a valvingarrangement incorporated in a single-acting hydraulic cylinder forcushioning the movement thereof as it approaches the end of itsoperating cycle.

A further object of this invention is to provide a valving arrangementfor a hydraulic cylinder that automatically controls the fluid flowtherein so as to reduce the speed of expansion and contraction of thecylinder as it approaches the end of its operating cycle.

A still further object of this invention is the provision of a valveassembly in a single-acting hydraulic cylinder that controls the returnof fluid exhaustion during the contracting cycle of the cylinder.

A yet further object of this invention is the provision of a multi-stagehydraulic cylinder having the final stage thereof continuously resistingexpansion of the cylinder so as to provide a cushioning effect.

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Other objects and advantages of the subject invention will be moreapparent from the following detailed description of the invention whentaken in conjunction with the drawings in which:

FIGURE 1 shows a rear dump vehicle incorporating a single-actingmulti-stage hydraulic cylinder made in accordance with the invention;

FIGURE 2 is an enlarged sectional view showing the details ofconstruction of the hydraulic cylinder;

FIGURE 3 is an enlarged view of the valving assembly which is associatedwith the final stage of the hydraulic cylinder shown in FIGURE 2;

FIGURE 4 is a view similar to FIGURE 3 but shows the positions of thevarious components of the valve as sembly at the initial expansion ofthe cylinder;

FIGURE 5 is a view similar to FIGURE 3 but shows the positions of thevarious parts just prior to the operation of the final stage of thehydraulic cylinder during the expansion cycle;

FIGURE 6 is a view of the final stage of the hydraulic cylinder justafter pressurized fluid has been directed thereto for contracting thehydraulic cylinder, and

FIGURE 7 is a view showing the final stage and the valving arrangementassociated therewith just prior to the complete contraction of thehydraulic cylinder.

Referring now to the drawings, FIGURE 1 shows a rear dump vehicle ofconventional design having a dump body 10 pivotally mounted to a vehiclefranie 12 for movement about a transverse axis indicated by the letterA. A single-acting multi-stage hydraulic cylinder 14 which i ".made inaccordance with the invention is connected between the vehicle frame 12and the underside of the dump body 10 for raising and lowering thelatter about the transverse axis. I

Referring now to FIGURE 2, the hydraulic cylinder 14 comprises acylindrical outer casing 16 which encloses a plurality of relativelymovable concentric cylinders 18, 20 and 22 and a rod portion 24 whichrespectively constitute the first, second, third and fourth stages ofthe cylinder assembly. The casing 16 of the hydraulic cylinder isprovided with a mounting 'eye portion 26 which is adapted to bepivotally anchored to the underside of the vehicle dump body 10. The rodportion 24 is also provided with a mounting eye portion 28 which ispivotally connected in a suitable manner to the vehicle frame 12 andrigidly secured to outer and inner concentric cylinder members 30 and32, both of which cooperate to define an annular fluid passage 33 withinthe rod portion 24 that communicates with an annular chamber 34 betweenthe third and fourth stages via ports 35 formed in cylinder member 30.The interior of cylinder member 32 forms a fluid passage 37 thatcommunicates with a port 38 formed in the eye portion 28. Similarly, thepassage 33 communicates with a port 40 also formed in the eye portion 28opposite the port 38. Oil lines 42 and 44 connect the respective portswith a control valve 46 which receives pressurized oil from a pump 48connected with a reservoir 50. The control valve 46 is constructed sothat it can selectively provide pressurized oil to one or the other lineor in the alternative to both lines simultaneously in a manner to bedescribed hereinafter.

As best seen in FIGURE 3, the rod portion 24 includes a sleeve valve 52which is slidably movable between two positions as limited by a lockring 54 and a shoulder 56 formed with the rod portion. The sleeve valve52 is formed as a cylinder and includes a pair of diametrically opposedand radially extending ports 58 which, as seen in FIGURE 3, are adaptedto register with corresponding openings 60 formed in the cylinder member32. A tubularshaped flow control valve 62 has one end thereofconcentrically located in the sleeve member 52 while the other end isguided for movement along the longitudinal axis of the assembly by aring 64 rigid with the inner cylinder membre 32. An annular stop 66 isfixed with the valve 62 intermediate the ends thereof and serves as aseat for one end of a coil spring 68 which rests on the ring 64 andcontinuously biases the valve 62 toward the right as seen in FIGURE 3. Asnap ring 70 is provided on the control valve 62 to limit the extent ofmovement of the latter due to the spring 68. It will also be noted thatfour oblong ports 72 are provided in the body of the valve 62 forpurposes which will be explained hereinafter.

As seen in FIGURES 2 and 3, the hydraulic cylinder isin a fullycollapsed or contracted position wherein the right end of the controlvalve 62 abuts and has the inner passage thereof blocked by a centrallylocated check valve assembly 74 that includes a boss 76 which forms aportion of the cylinder and extends from and is rigidly bolted to thecylinder casing 16. The boss 76 is suitably bored and serves toaccommodate a ball valve 78 which is normally seated to close a port 80which serves to direct pressurized oil from the port 38 and passage 37to the head end of the hydraulic cylinder via radially extending ports82 formed in the side walls of the boss.

The hydraulic cylinder assembly 14 operates as follows: As seen inFIGURES 2 and 3, the hydraulic cylinder 14 is in the fully collapsedposition with the flow control valve 62 engaging the boss 76 and thesleeve valve 52 having its ports 58 aligned with the ports 60 formed inthe cylinder member 32. At such time, the dump body is in the loweredposition and when the operator desires the dump body to be raised, thecontrol valve 46 is moved to the raised position so that pressurizedfluid is directed through lines 42 and 44 into the hydraulic cylinderinterior. Thus, as indicated by the arrows in FIGURE 4, the pressurizedfluid flows through the rod portion 24 and the flow control valve 62 tounseat the ball 78 so that the fluid is directed to the piston headportion of the cylinder assembly. Simultaneously, the sleeve valve 52 isshifted toward the right to block off communication between the ports 58and 60. As a result, the upper end of the casing 16 moves away from therod portion 24 and sequentially causes extension of the first, second,and third stages in that order. As seen in FIGURE 5, the valve 62 movesout of the rod portion 24 under the influence of the coil spring 68 andthis movement of the valve continues until the lock ring 70 engages thesupport ring 64. It will also be noted that as the third stage orcylinder 22 is extended, the piston portion thereof acts against thepressurized fluid supplied to chamber 34 through passage 33 and ports35. Therefore, as the hydraulic cylinder approaches the final phase ofits extension which would normally occur as the center of gravity of theload moves to the right of a vertical line passing through the pivotaxis A or, in other words, when the dump body moves overcenter, theusual damaging pull on the hydraulic cylinder is substantiallyeliminated by the cushioning effect which is provided by the linepressure in the chamber 34.

After the dump body 10 is fully raised, it can be lowered by moving thecontrol valve 46 to the powerdown position at which time fluid isdirected to the hydraulic cylinder through line 44 only with line 42serving as a vent to reservoir 50. Thus, as seen in FIGURE 6, the fluidflows as indicated by the arrows so as to cause the fourth stage or therod portion 24 to move into the third stage or cylinder 22 at a slowrate until the center of gravity of the dump body moves overcenter or tothe left of the imaginary vertical line through pivot axis A. At thesame time, the sleeve valve 52 reassumes its original position whereinits ports 58 register with the ports 60 so that oil can flow frompassage 37 to chamber 34. Thus, any accelerated collapsing movement ofthe hoist assembly does not result in a vacuum being formed in thechamber 34 or the other chamber between the cylinders. As the hydrauliccylinder app-roaches its fully collapsed or contracted position, theflow control valve 62 is again engaged by the boss 76 of the check valvearrangement 74 as seen in FIGURE 7 and the existing fluid causes theball 78 to close port 80. Hence, the rate of collapsing movement of thehydraulic cylinder is immediately decreased inasmuch as the fluid at thepiston head end can exit only through the slots 72 in the fluid controlvalve 62. Thus, as the casing 16 of the hydraulic cylinder continues tomove toward the fourth stage, flow restriction of the existing fluidslowly increases as the fluid control valve 62 moves further into thefourth stage with the result that a cushioning effect is realized as thedump body approaches the fully lowered position.

I claim:

1. In combination, a hydraulic cylinder having relatively movable pistonand cylinder members, a first fluid passage in said piston memberserving to connect a source of pressurized fluid with the piston headend of the cylinder for expanding the latter and also serving as anexhaust passage, a second fluid passage and porting formed in saidpiston member serving to continuously connect said source of pressurizedfluid with the rod end of said piston head for cushioning the piston ofsaid cylinder during the expansion thereof, and a valve assemblyincluding a spring biased tubular valve member slidably mounted in saidfirst passage, said valve having elongated slots formed therein andhaving an open end engaged and blocked by a portion of the cylinder forclosing the normal flow through said valve and for urging the latterinto said first passage so that fluid from the piston head end of thecylinder is exhausted through said elongated slots at a decreasing rateas the cylinder contracts so as to provide a cushioning eflect.

2. In combination, a single-acting hydraulic cylinder having relativelymovable piston and cylinder members, a fluid passage in said pistonmember serving to connect a source of pressurized fluid with the pistonhead end of the cylinder for expanding the latter and also serving as anexhaust passage during the contraction of the cylinder, cushioning meansfor decreasing the speed of cylinder contraction, said cushioning meanscomprising a tubular flow control valve member slidably mounted in saidpassage and having a plurality of elongated slots formed therein, meansbiasing said flow control valve whereby the elongated slots are locatedoutside of the passage when the cylinder is in the expanded position,and means formed on the cylinder for blocking an open end of the flowcontrol valve to close the normal flow through the flow control valveand for urging the latter against the influence of said biasing meansinto said passage so that fluid from the piston head end of the cylinderis exhausted through the elongated slots at a decreasing rate as thecylinder contracts.

3. The hydraulic cylinder of claim 2 wherein said means biasing saidflow control valve is a spring.

4. The hydraulic cylinder of claim 2 wherein said slots are formed withtheir major axes substantially parallel to the longitudinal axis of saidflow control valve.

5. The hydraulic cylinder of claim 2 wherein said means on said cylinderfor closing normal flow comprises a boss having an outer diametergreater than the inner diameter of said flow control valve.

6. The hydraulic cylinder of claim 5 wherein said boss has a ball checkarrangement for permitting fluid to flow therethrough only duringexpansion of said cylinder.

7. In combination, a hydraulic cylinder having relatively movable pistonand cylinder members, a first fluid passage in said piston memberserving to connect a source of pressurized fluid with the piston headend of the cylinder for expanding the latter and also serving as anexhaust passage during contraction of the cylinder, a second fluidpassage and porting formed in said piston member serving to continuouslyconnect said source of pressurized fluid with the rod end of the pistonhead for cushioning the piston during expansion of the cylinder,cushioning means located in said first fluid passage for decreasing thespeed of cylinder contraction, said cushioning means comprising atubular flow control valve member slidably mounted in said first passageand having a plurality of slots formed therein, means biasing said flowcontrol valve whereby the slots are located outside the associatedpassage when the cylinder is in the expanded position, a boss formed onthe cylinder for blocking an open end of the flow control valve to closethe normal flow through the flow control valve and for urging the latteragainst the influence of the biasing means into said passage so thatfluid from the piston head end of the cylinder is exhausted through theslots at a decreasing rate as the cylinder contracts, and meansincluding a sleeve valve connecting said first passage with said secondpassage and permitting fluid to flow therebetween and to said rod end ofthe cylinder through said porting so as to make up any deficiency influid in said rod end of the cylinder while the latter is contracting.

References Cited UNITED STATES PATENTS 845,827 3/ 1907 Steedman 92852,293,167 8/1942 Overbeke 92-113 X 2,497,489 2/1950 Coursen et al. 92852,676,573 4/1954 Abbe 92-52 X 2,730,401 1/1956 Rea 91--441 X 2,778,3431/1957 Crosetto et a1. 91-407 X 2,800,234 7/1957 Herpich et a1. 9253 X2,897,791 8/1959 Routledge 9253 X 2,922,398 1/ 1960 Lindsey 9285 X3,088,530 5/1963 Feucht 92112 X 3,162,092 12/1964 Corwin 91-407 X3,232,180 2/1966 Deschenes 94-422 3,259,026 7/1966 Madland et al 91422 XMARTIN P. SCHWADRON, Primary Examiner.

I. C. COHEN, Assistant Examiner.

US. Cl. X.R.

